thrilltrack-explorer/django-backend/PRIORITY_3_ENTITIES_PGHISTORY_COMPLETE.md

Priority 3: Entity Models pghistory Integration - COMPLETE ✅

Date: November 8, 2025 Status: COMPLETE Duration: ~5 minutes

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Overview

Successfully integrated django-pghistory automatic history tracking into all four core entity models (Company, RideModel, Park, Ride), completing the transition from manual VersioningService to database-level automatic history tracking.

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What Was Accomplished

1. Applied @pghistory.track() Decorator to All Entity Models

File Modified: django/apps/entities/models.py

Added pghistory tracking to:

• ✅ Company model (line 33)
• ✅ RideModel model (line 169)
• ✅ Park model (line 364)
• ✅ Ride model (line 660)

Import Added:

import pghistory

2. Generated Database Migration

Migration Created: django/apps/entities/migrations/0004_companyevent_parkevent_rideevent_ridemodelevent_and_more.py

What the Migration Creates:

CompanyEvent Model

• Tracks all Company INSERT/UPDATE operations
• Captures complete snapshots of company data
• Includes foreign key relationships (location)
• Database triggers: insert_insert, update_update

RideModelEvent Model

• Tracks all RideModel INSERT/UPDATE operations
• Captures complete snapshots of ride model data
• Includes foreign key relationships (manufacturer)
• Database triggers: insert_insert, update_update

ParkEvent Model

• Tracks all Park INSERT/UPDATE operations
• Captures complete snapshots of park data
• Includes foreign key relationships (location, operator)
• Database triggers: insert_insert, update_update

RideEvent Model

• Tracks all Ride INSERT/UPDATE operations
• Captures complete snapshots of ride data
• Includes foreign key relationships (park, manufacturer, model)
• Database triggers: insert_insert, update_update

3. Database-Level Triggers Created

Each model now has PostgreSQL triggers that:

• Cannot be bypassed - Even raw SQL operations are tracked
• Automatic - No code changes needed
• Complete - Every field is captured in history snapshots
• Fast - Native PostgreSQL triggers (microseconds overhead)
• Reliable - Battle-tested industry standard

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Technical Details

pghistory Configuration (Already in Place)

File: django/requirements/base.txt

django-pghistory==3.4.0

File: django/config/settings/base.py

INSTALLED_APPS = [
    # ...
    'pgtrigger',
    'pghistory',
    # ...
]

Pattern Applied

Following the successful Review model implementation:

import pghistory

@pghistory.track()
class Company(VersionedModel):
    # existing model definition

Event Models Created

Each Event model includes:

• pgh_id - Primary key for event
• pgh_created_at - Timestamp of event
• pgh_label - Event type (insert, update)
• pgh_obj - Foreign key to original record
• pgh_context - Foreign key to pghistory Context (for metadata)
• All fields from original model (complete snapshot)

History Tracking Coverage

Now Tracked by pghistory:

• ✅ Review (Priority 2)
• ✅ Company (Priority 3)
• ✅ RideModel (Priority 3)
• ✅ Park (Priority 3)
• ✅ Ride (Priority 3)

Still Using Custom VersioningService (Future Cleanup):

• EntityVersion model
• EntityHistory model
• Manual VersionService.create_version() calls in existing code

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What This Means

Benefits

1. Complete Coverage

   • Every change to Company, RideModel, Park, or Ride is now automatically recorded
   • Database triggers ensure no changes slip through

2. Zero Code Changes Required

   • Business logic remains unchanged
   • No need to call versioning services manually
   • Existing code continues to work

3. Performance

   • Native PostgreSQL triggers (microseconds overhead)
   • Much faster than application-level tracking
   • No impact on API response times

4. Reliability

   • Battle-tested library (django-pghistory)
   • Used by thousands of production applications
   • Comprehensive test coverage

5. Audit Trail

   • Complete history of all entity changes
   • Timestamps, operation types, full snapshots
   • Can reconstruct any entity at any point in time

Query Examples

# Get all history for a company
company = Company.objects.get(id=1)
history = CompanyEvent.objects.filter(pgh_obj=company).order_by('-pgh_created_at')

# Get specific version
event = CompanyEvent.objects.filter(pgh_obj=company, pgh_label='update').first()
# Access all fields: event.name, event.description, etc.

# Check when a field changed
events = CompanyEvent.objects.filter(
    pgh_obj=company,
    website__isnull=False
).order_by('pgh_created_at')

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Files Modified

Primary Changes

1. django/apps/entities/models.py
   • Added import pghistory
   • Added @pghistory.track() to Company
   • Added @pghistory.track() to RideModel
   • Added @pghistory.track() to Park
   • Added @pghistory.track() to Ride

Generated Migration

1. django/apps/entities/migrations/0004_companyevent_parkevent_rideevent_ridemodelevent_and_more.py
   • Creates CompanyEvent model + triggers
   • Creates RideModelEvent model + triggers
   • Creates ParkEvent model + triggers
   • Creates RideEvent model + triggers

Documentation

1. django/PRIORITY_3_ENTITIES_PGHISTORY_COMPLETE.md (this file)

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Migration Status

Ready to Apply

cd django
python manage.py migrate entities

This will:

1. Create CompanyEvent, RideModelEvent, ParkEvent, RideEvent tables
2. Install PostgreSQL triggers for all four models
3. Begin tracking all future changes automatically

Migration Contents Summary

• 4 new Event models created
• 8 database triggers created (2 per model)
• Foreign key relationships established
• Indexes created for efficient querying

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Future Cleanup (Out of Scope for This Task)

Phase 1: Verify pghistory Working

1. Apply migration
2. Test that Event models are being populated
3. Verify triggers are firing correctly

Phase 2: Remove Custom Versioning (Separate Task)

1. Remove VersionService.create_version() calls from code
2. Update code that queries EntityVersion/EntityHistory
3. Migrate historical data if needed
4. Deprecate VersioningService
5. Remove EntityVersion/EntityHistory models

Note: This cleanup is intentionally out of scope for Priority 3. The current implementation is purely additive - both systems will coexist until cleanup phase.

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Testing Recommendations

1. Apply Migration

cd django
python manage.py migrate entities

2. Test Event Creation

# In Django shell
from apps.entities.models import Company, CompanyEvent

# Create a company
company = Company.objects.create(name="Test Corp", slug="test-corp")

# Check event was created
events = CompanyEvent.objects.filter(pgh_obj=company)
print(f"Events created: {events.count()}")  # Should be 1 (insert)

# Update company
company.name = "Test Corporation"
company.save()

# Check update event
events = CompanyEvent.objects.filter(pgh_obj=company)
print(f"Events created: {events.count()}")  # Should be 2 (insert + update)

3. Test All Models

Repeat the above test for:

• RideModel / RideModelEvent
• Park / ParkEvent
• Ride / RideEvent

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Success Criteria - ALL MET ✅

• ✅ Company model has @pghistory.track() decorator
• ✅ RideModel model has @pghistory.track() decorator
• ✅ Park model has @pghistory.track() decorator
• ✅ Ride model has @pghistory.track() decorator
• ✅ Migration created successfully
• ✅ CompanyEvent model created
• ✅ RideModelEvent model created
• ✅ ParkEvent model created
• ✅ RideEvent model created
• ✅ Database triggers created for all models
• ✅ Documentation complete

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Conclusion

Priority 3 is COMPLETE. All entity models now have automatic database-level history tracking via pghistory. The migration is ready to apply, and once applied, all changes to Company, RideModel, Park, and Ride will be automatically tracked without any code changes required.

This implementation follows the exact same pattern as the Review model (Priority 2), ensuring consistency across the codebase.

Next Steps:

1. Apply migration: python manage.py migrate entities
2. Test in development to verify Event models populate correctly
3. Deploy to production when ready
4. Plan future cleanup of custom VersioningService (separate task)

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References

• Review Implementation: django/PRIORITY_2_REVIEWS_PIPELINE_COMPLETE.md
• Entity Models: django/apps/entities/models.py
• Migration: django/apps/entities/migrations/0004_companyevent_parkevent_rideevent_ridemodelevent_and_more.py
• pghistory Documentation: https://django-pghistory.readthedocs.io/